Alkaline Bleach-Fix with Ferric Ammonium EDTA?

Discussion in 'B&W: Film, Paper, Chemistry' started by processreversal, Mar 25, 2013.

  1. processreversal

    processreversal Member

    Messages:
    7
    Joined:
    Mar 25, 2013
    Shooter:
    Multi Format
    Hi,

    I'm curious if anyone happens to know whether it's possible to formulate an alkaline bleach-fix using Ferric Ammonium EDTA as the primary bleaching agent.

    Cheers...
     
  2. Rudeofus

    Rudeofus Subscriber

    Messages:
    2,570
    Joined:
    Aug 13, 2009
    Shooter:
    Medium Format
    What's the pH you are aiming for?
     
  3. processreversal

    processreversal Member

    Messages:
    7
    Joined:
    Mar 25, 2013
    Shooter:
    Multi Format
    Originally, I was aiming for 7.5-8.5; but now I'm just curious if it's possible at any alkalinity.
     
  4. processreversal

    processreversal Member

    Messages:
    7
    Joined:
    Mar 25, 2013
    Shooter:
    Multi Format
    Sorry, I guess 'alkalinity' isn't the best word to use there. Let's just say any pH above 7, but ideally something that isn't caustic.

    I've done a few test before doing simple substitutions from a formula that originally specified acetic acid, but obviously there wasn't any activity to the solution.

    I would also be interested if it is possible to formulate a rehalogenating bleach using any EDTA salt in an alkaline environment.
     
  5. Rudeofus

    Rudeofus Subscriber

    Messages:
    2,570
    Joined:
    Aug 13, 2009
    Shooter:
    Medium Format
    Watch out for nasty Ammonia smell at pH 8 ...

    Since you started this thread in the b&w forum: what are you trying to bleach?
     
  6. Gerald C Koch

    Gerald C Koch Member

    Messages:
    6,248
    Joined:
    Jul 12, 2010
    Location:
    Southern USA
    Shooter:
    Multi Format
    Why do you feel that the blix should be alkaline? Cemically there would be no advantage in doing this. There is the possibility of the iron III hyydrolysing and coming out of solution when the pH goes above 7.
     
  7. processreversal

    processreversal Member

    Messages:
    7
    Joined:
    Mar 25, 2013
    Shooter:
    Multi Format
    The film I'm bleaching in KODAK 7366 Tri-X Reversal (i.e. Black and White 16mm motion picture film) processed as reversal. The film has not, however been processed in the conventional manner. Instead of...

    First Developer
    Bleach (Dichromate/Sulfuric)
    Clear
    Second Developer
    Fix

    I decided to process the footage as such:

    Developer
    In-direct Toner
    Bleach (rehalogenating)
    Fix

    ...a reversal by toner sort-of-speak.

    The process worked fine with a conventional ferricyanide bleach, but care had to be exercised so as to avoid having the bleach destroy the positive image. This is because ferricyanide does a poor job differentiating between the toned image and the untoned image (and for similar reasons, ferricyanide isn't used in color chemistry, which eventually led to the use of ferric ammonium EDTA...and so forth)

    Therefore, I began using a ferric ammonium EDTA based Bleach-Fix's and ended up with this process:

    First Dev
    Indirect Toner
    Blix

    For the most part, I'm satisfied with the process, but for "less-than-scientific reasons," I was interested in keeping the entire process alkaline; specifically, the alkalinity of sea-water...
     
  8. processreversal

    processreversal Member

    Messages:
    7
    Joined:
    Mar 25, 2013
    Shooter:
    Multi Format
    Right, that's what I was thinking... Is that the case with all EDTA salts? Do they only remain stable in acids?
     
  9. Gerald C Koch

    Gerald C Koch Member

    Messages:
    6,248
    Joined:
    Jul 12, 2010
    Location:
    Southern USA
    Shooter:
    Multi Format
    The hydrolysis has nothing to do with the EDTA it is a problem with iron salts. Metal bleachs, iron, manganese, chromium, and copper will not work in alkaline solution. The correcponding metal hydrated oxides will precipitate out of solution.
     
    Last edited by a moderator: Mar 25, 2013
  10. Gerald C Koch

    Gerald C Koch Member

    Messages:
    6,248
    Joined:
    Jul 12, 2010
    Location:
    Southern USA
    Shooter:
    Multi Format
    Is there a particular reason to use an indirect toner?
     
  11. processreversal

    processreversal Member

    Messages:
    7
    Joined:
    Mar 25, 2013
    Shooter:
    Multi Format
    It needs to be an indirect toner so that it only affects the remaining silver halides after the first development. The bleach following, therefore, should only remove the silver reduced by the first development, leaving us with a (toned) positive image.

    As for the hydrolysis theory, I'm curious than why potassium ferricyanide seems to remain stable in an alkaline environment. Would you say that there is a rate of oxidization?
     
  12. Photo Engineer

    Photo Engineer Subscriber

    Messages:
    25,781
    Joined:
    Apr 19, 2005
    Location:
    Rochester, NY
    Shooter:
    Multi Format
    Ferric Ammonium EDTA loses oxidation potential as pH becomes more alkaline than about 6.7. It stops bleaching. As you continue to raise the pH, the Ferric ion begins to precipitate out as Ferric Hydroxide and you lose all oxidation power completely. Basically, you end up with a slurry of glop that stinks like ammonia.

    BTDT.

    PE
     
  13. Gerald C Koch

    Gerald C Koch Member

    Messages:
    6,248
    Joined:
    Jul 12, 2010
    Location:
    Southern USA
    Shooter:
    Multi Format
    The basic 5 steps of reversal processing are

    1. First developer
    2. Bleach (non-halogenating)
    3. Re-exposure *
    3. Second developer (may be a fogging developer)
    5. Fixer

    * Re-exposure is not required if a fogging developer is used.

    There are also washes and a clearing bath but these are the basic steps.

    Note that a rehalogenizing bleach is not used as it defeats the purpose. You do not want the image procuced by the first developer when bleached to be sensitive to light.

    For specific information go to the following site. Be sure to click on the last line "REVERSAL PROCESSING" for full information. http://www.ilfordphoto.com/applications/page.asp?n=90
     
    Last edited by a moderator: Mar 25, 2013
  14. Rudeofus

    Rudeofus Subscriber

    Messages:
    2,570
    Joined:
    Aug 13, 2009
    Shooter:
    Medium Format
    Just curious which indirect toning technique you plan on using. Unless you use very special dyes you shouldn't have an issue with acid, and if you thoroughly tone with Sulfide neither acid nor ferricyanide should be a problem. I suspect you want to red or blue tone, and some of the resulting compounds will be attacked by ferricyanide. If that is indeed the case, you should be able to work with Ammonium Ferric EDTA based BLIX regardless of pH.
     
  15. Gerald C Koch

    Gerald C Koch Member

    Messages:
    6,248
    Joined:
    Jul 12, 2010
    Location:
    Southern USA
    Shooter:
    Multi Format
    If, as Rudeofus mentions, you wish to use a dye toner it is better to do this after the reversal process.
     
  16. processreversal

    processreversal Member

    Messages:
    7
    Joined:
    Mar 25, 2013
    Shooter:
    Multi Format
    The indirect toner I'm using could be any true toner (i.e. one that converts the silver grains formed in the first developer to a different metallic grain such as selenium, iron or silver-sulfide).

    A dye toner (or tinter) does not actually convert the silver to a new metal; instead, the bleach (or mordant in this case) simply allows the dyes to bound to the grains which would otherwise have no affinity to them. Therefore, using a tinter would not be as viable since the silver grains that represent our positive image would still be susceptible to the blix. The resulting image, therefore, would be solely formed of the dyes which simply do not have enough density on there to be pictorially pleasant.

    Your right though that the pH isn't an issue. That was never really an issue. In fact, I've already processed some 5,000 feet with the process using an acid-based BLIX. Here's a sample to give you an idea: http://vimeo.com/51802644.

    However, despite how the process works, I wanted to see if I could go further with it and maintain the entire process at a specific alkalinity, which according to PE, isn't possible - or at least with the bleach agent at hand...